Devices that enable high-precision determination of the amount and location of the imbalance of a tool holder are known, for example, from the German patent application DE 102 33 917 A1.
Once the amount and location of the imbalance have been determined, it is also known to remove some material from a suitable location on the tool holder in order to thus permanently balance the tool holder.
As a rule, the tool holder is unclamped from the balancing machine for this purpose and the necessary amount of material is removed from the predetermined location. The tool holder is then clamped back into the balancing machine to perform a test measurement. The unclamping and reclamping is time-consuming and may compromise measurement accuracy since it is always a possibility that in the course of the reclamping, the tool holder will assume a slightly different position than in the first clamping.
Internally, this has therefore already led to the thought of leaving the tool holder clamped while it is machined in a material-removing way in order to balance it. To this end, the spindle unit must be immobilized so that the forces and vibrations occurring in the course of the material-removing machining do not damage the highly sensitive measuring sensors or the spindle mount of the measuring unit. Furthermore, the spindle unit could move out of the way of the material-removing tool and thus compromise the precision of the material removal if it were not locked in place. Another possibility that has been considered is to achieve this locking function by placing clamping jaws against the spindle unit from two sides, which clamp it between themselves like an external brake drum. Such an approach, however, exerts stress at least on the sensors and therefore also results in measurement inaccuracies.
Furthermore, a clamping device that is attached directly to the spindle unit also prevents a rotary motion of the spindle. Such a rotary motion, however, can be entirely desirable and necessary in certain types of material removal, for example milling a groove along the outer circumference of the test piece.
The object of the invention is to disclose a device with which the rotational imbalance of a tool holder can be determined and eliminated, without having to put up with the problems mentioned above.